NEW DELHI : Indian stocks extended their rally on Monday, led by gains in HDFC twin stocks and strong buying activity in other index heavyweights. Buoyed by gains in the US market, local stocks saw a gap-up opening on Monday. Favourable economic data and sustained foreign fund inflows propelled the Sensex beyond 65,000, with the Nifty 50 surpassing 19,300, maintaining the bullish trend. The Sensex, which closed above 64,000 on Friday, ended trading on Monday at 65,205.05, gaining 0.75%. With gains of 0.7%, the Nifty 50 ended the day at 19,322.55, close to the all-time high of 19,345.10 that it…